If the server crashes
or otherwise fails to put the keyboard back in ascii mode when it exits,
it can leave your keyboard dead. If you are able to login remotely, you
can reset it typing:

kbd_mode -a

Conversely, changing the keyboard to ascii mode while the server is running
will make the keyboard appear to be dead while the the mouse continues
to work. Again, if you are able to login remotely, you can reset it typing: